Thank you Ujjawal for responding.

Since my instance is still on Helsinki, I was not able to find the roles "snc_external" and "snc_internal".

What ultimately solved my problem was modifying the access control for "read", for that table, and adding logic that checked if the current user is listed on a specific field.

Your link was very helpful in that it led me to investigate ACLs, which up until now, I have yet to touch.   I'm still a newbie admin/developer. 😃